New Delhi , India -LRB- CNN -RRB- -- India 's prime minister said he has nothing to hide and would be `` happy '' to appear before a parliamentary panel looking into a multi-billion dollar telecom scandal .

`` I wish to state categorically that I have nothing to hide from the public at large , and as a proof of my bona fides , I intend to write to the chairman of the Public Accounts Committee that I shall be happy to appear before the PAC if it chooses to ask me to do so , '' Prime Minister Manmohan Singh said in a speech at a national meeting of the ruling Congress party .

`` I sincerely believe that , like Caesar 's wife , the prime minister should be above suspicion , and it is for this reason that I am prepared to appear before the PAC even though there is no precedent to this effect . ''

Opposition parties have stepped up their attacks on Singh , hailed as the father of India 's economic reforms , since the country 's main auditor reported in November that a sale of a second-generation wireless spectrum two years ago had been carried out at below-market prices .

According to the government audit , the treasury lost up to $ 31 billion from under-valuation of airwaves .

The alleged scam , seen as the biggest to hit India in recent times , has forced the country 's Telecom Minister A. Raja , to step down . Raja , member of a key regional ally of Singh 's Congress party , denies the charges .

But opposition lawmakers are seeking a larger probe into the 2008 phone-license awards , and accuse Singh of having not acted swiftly .

India 's prime minister , on his part , insists the wrongdoers will be punished .

`` It is my promise to you that no guilty person will be spared -- whether he is a political leader or a government official , whichever party he may belong to and howsoever powerful he may be , '' Singh said Monday .

The damning audit report came on the heels of allegations of massive fraud in sports and real estate .

Investigators are already probing complaints of financial malfeasance in the Commonwealth Games that India hosted in October .

And several politicians , military officials and bureaucrats are the subjects of a separate inquiry for allegedly taking apartments meant for war-widows .

CNN 's Harmeet Shah Singh contributed to this report .

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Opposition parties have stepped up their attacks on Singh

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An audit shows government sold airwaves at under value

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The audit follows massive fraud in sports and real-estate